This invention is in the field of electrical relays for controlling external circuits.
It has been proposed to provide relays or circuit controlling apparatus relying on the change of shape of thermally responsive bimetallic elements. However, in general, such devices have been of such nature that the external circuit is controlled in the desired manner only as long as heat is supplied to the thermally responsive elements. In this regard, see the following patents:
U.S. Pat. No. 2,769,938, Pauly; PA1 U.S. Pat. No. Re. 22,973, Kurtz; PA1 U.S. Pat. No. 3,551,868, Good; PA1 U.S. Pat. No. 2,446,831, Hottenroth, Jr.; PA1 U.S. Pat. No. 2,324,161, Holmes; PA1 U.S. Pat. No. 2,914,644, Holtkamp; PA1 British Pat. No. 830,157.
In the above patents, an electrical heater heats a bimetallic element to cause it to change shape and thereby open or close contacts for controlling an external circuit. However, as understood, none of the above patents disclose an arrangement that is simple in construction and yet is stable in either of its on or off positions without maintaining current through the electrical heaters.